Conventionally, a receiver in a cellular radio communication system includes a receiving filter making it possible to select the main channel assigned to it.
However, the presence of multiple paths between a transmitter and a receiver, or the presence of other users in the same cell, causes interfering signals, necessitating the use of a complex filtering technique at the reception.
A filtering technique based on a MMSE (“Minimum Mean Square Error”) receiver has been envisaged, as shown in FIG. 1.
According to this technique of the prior art, a stationary receiving filter Rx 13 is considered. Thus, the filter Rx 13 is designed so as to comply with a certain frequency template.
More specifically, this receiving filter Rx 13 is suitable for eliminating the contribution of an additive white Gaussian noise AWGN 12 added during the transmission on the main signal x(k), the main signal being filtered by a global filter H 11 representing the different processing operations performed.
The receiving filter Rx 13 is then designed so as to minimise the decision error between the signal y(k) at the output of the filter Rx 13 and the main signal x(k) before transmission.
Thus, the MMSE receiving filter Rx 13 takes into account the global filter H 11, and is designed so as to minimise the mean square error at the output of this filter Rx 13, defined by:J(H)=E[|x(k)−y(k)|2]where E[•] corresponds to the mathematical expectation.
However, a major disadvantage of this technique is that the receiving filter is not designed by taking into consideration the spectrum of signals interfering with the main signal, and does not therefore achieve the best compromise between the inter-symbol and inter-user interference.
Thus, this technique can eliminate only a limited inter-symbol interference coming from the different filters, such as the filter H 11, and does not take into account the interferences coming, for example, from other users, also called co-channel or adjacent interference.